【flutter查看大图(可缩放、放大后可拖拽、保存到本地)】

在Flutter中，你可以使用flutter_swiper_plus插件来查看大图，并结合photo_view插件实现图片的缩放和保存功能。以下是一个简单的示例代码：

首先，在pubspec.yaml中添加依赖：

dependencies:
  flutter:
    sdk: flutter
  flutter_swiper_plus: ^2.0.1
  photo_view: ^0.13.2

然后，在你的Flutter代码中使用这些插件：

import 'package:flutter/material.dart';
import 'package:flutter_swiper_plus/flutter_swiper_plus.dart';
import 'package:photo_view/photo_view.dart';
import 'package:photo_view/photo_view_gallery.dart';
import 'package:path_provider/path_provider.dart';
import 'package:flutter/services.dart';
import 'package:flutter_downloader/flutter_downloader.dart';
import 'package:path/path.dart' as Path;
 
void main() {
  runApp(MyApp());
}
 
class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: GallerySwiper(),
    );
  }
}
 
class GallerySwiper extends StatefulWidget {
  @override
  _GallerySwiperState createState() => _GallerySwiperState();
}
 
class _GallerySwiperState extends State<GallerySwiper> {
  List<String> images = [
    'https://example.com/image1.jpg',
    'https://example.com/image2.jpg',
    // ...
  ];
 
  void downloadImage(String imageUrl) async {
    final taskId = await FlutterDownloader.enqueue(
      url: imageUrl,
      savedDir: (await getExternalStorageDirectory()).path,
      fileName: 'image.jpg',
      openFileFromNotification: true,
    );
    print("Download Image with id: $taskId");
  }
 
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SwiperPlus(
        items: images.map((imgUrl) => SwiperPluginImage(imageUrl: imgUrl)).toList(),
        scrollDirection: Axis.horizontal,
        viewportFraction: 1,
        scale: 1.0,
        onTap: (index) {
          Navigator.push(
            context,
            MaterialPageRoute(
              builder: (context) => PhotoViewGallery.builder(
                scrollDirection: Axis.horizontal,
                itemCount: images.length,
                builder: (context, index) {
                  return PhotoViewGalleryPageOptions(
                    imageProvider: NetworkImage(images[index]),
                    initialScale: PhotoViewComputedScale.contained * 1,
                    minScale: PhotoViewComputedScale.contained * 1